The present invention relates to a thin-film transistor (referred to as TFT) display device and, more specifically, to art which can be effectively utilized in a device in which a display panel of a TFT active matrix constitution and a drive circuit therefor are formed on a glass substrate.
When a TFT display device is realized in a small size, the numerical aperture becomes too small with the conventional system in which a thin amorphous silicon film is used as a channel layer of transistors. This is because, since limitation exists in the characteristics of the transistors, it is not allowed to decrease the size of the transistors.
When the transistors are formed by using the thin amorphous silicon film, furthermore, it becomes necessary to provide a peripheral drive circuit on the outside since performance of the transistors are not sufficient to drive a display device.
When the transistors are formed by using a polycrystalline silicon (referred to as poly-Si) film, it is possible to drive a display device and a drive circuit has also been formed on the same glass substrate.
The TFT elements using a poly-Si film have been used for constituting a color view finder of a small video camera having a number of pixels of about 100,000 and a diagonal length of the display area of 0.7 inches. Study has been made to utilize the TFT display device having poly-Si film as a light valve of a projector or as a panel for a head-mounted (spectacle-type) display designed for accomplishing virtual reality. The TFT display device utilizing the poly-Si film has been disclosed in, for example, "Nikkei Electronics" published by Nikkei-McGraw-Hill Co., Feb. 28, 1994, pp. 103-109.